Actually use EGLint - EGLconst does not exist.

This fixes a build error introduced by commit with change id:
I3ace17447aa9a83655b6fa6b4246a6a16592936c and git hash
33bbdb88216e72bcc3149f52e7a961609f5406a0.

Change-Id: I548866c1e0958811f66bc4b5d7f048822e59274c
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>
Reviewed-by: Pasi Petäjäjärvi <pasi.petajajarvi@digia.com>